Life cycle of dwellings; a conceptual model based on Dutch practice

What is the average lifespan of dwellings? Many professionals answer this question with presumptions of the pre-calculated write off time in the rental sector (50 years). The true answer should be though, that we do not know it: the average age of the actual housing stock - at least in most `old¿ EU countries - being too young for useful longitudinal ex post analyses. Looking at the actual rate of new construction of approximately 1% pro annum the average needed lifespan of the existing dwelling stock should be at least 1 century. Looking at the actual replacement rate of less than 0,25% pro annum the average needed lifespan of the existing Dutch dwelling stock should be at least 4 centuries! Recent research shows that, from a sustainable viewpoint, life cycle extension of existing dwellings is a better choice than replacement by new construction (de Jonge, 2005; Klunder, 2005). However, when we look at recent schemes proposed by Dutch housing associations we can see a sharp increase in numbers of less than 50 years old dwellings to be demolished. What is happening and how can we assess this increase. Unlike the life span of human beings, the life span of dwellings can technically be endless; prolongation is subject to decisions of the owner. The knowledge about this decision process and the underlying considerations is meagre (p.m.). Following our previous research (Van der Flier en Thomsen, 2004; Thomsen, 2005), our paper gives an overview of contemporary knowledge about the life cycle of dwellings and a conceptual framework to analyse the decision process about (the prolongation of) the life span of dwellings. We will use this scheme to assess the schemes proposed by Dutch housing associations and end with some questions for further research.